Remove queue-size tasks instead of setting to zero

Author: EpicWink

Lib/queue.py

@@ -238,9 +238,10 @@ def shutdown(self, immediate=False):
         with self.mutex:
             self.is_shutdown = True
             if immediate:
+                n_items = self._qsize()
                 while self._qsize():
                     self._get()
-                self.unfinished_tasks = 0
+                self.unfinished_tasks -= n_items
                 self.not_empty.notify_all()
                 # release all blocked threads in `join()`
                 self.all_tasks_done.notify_all()